Expression of an intracisternal A-particle-like element in rat ovary

Expression of human endogenous gammaretroviral sequences in endometriosis and ovarian cancer

Endogenous retroviruses (ERVs) probably originate from ancient germ cell infections by exogenous retroviruses. A high expression of retroviruses in reproductive tissue increases the risk of viral transmission to germ line cells. We therefore investigated the expression of human ERVs (HERVs) in normal endometrium, endometriosis, normal ovaries, and ovarian cancer. Four real-time PCRs (QPCRs) for HERV-E, HERV-I/T, HERV-H, and HERV-W, respectively, and an expression control gene were used. HERV-E RNA expression was significantly higher in endometriotic tissue (average, SD) than in normal endometrium (average, SD), both measured as ratios versus control gene expression and as. HERV-E and HERV-W RNA were higher in normal ovarian tissue than in ovarian cancer. This illustrates that HERV expression is not automatically higher in malignant tissues. The other HERV PCRs did not show expression patterns as distinctive as HERVE and HERV-W in the two kinds of reproductive tissue. A small number of candidate HERV-E loci from which the transcription took place were identified by sequencing of amplimers. The role of HERV-E and HERV-W in endometriosis merits further investigation.

Endogenous retroviruses and animal reproduction

Endogenous retroviruses (ERV), as part of the host genetic heritage, are transmissible to the next generation in a Mendelian way. Their abundance in animal genomes and their expression primarily detected in germ cells, embryonic tissues and cancer cell lines, raised the question of their biological significance. This article reviews the possible role of ERVs in the physiology and diseases of animal reproduction, from Drosophila to human. In males, there is no trivial involvement of ERVs in a physiological process. Conversely, a spermatogenesis defect was associated in the human male with HERV-K expression and HERV15-induced chromosomal alteration, leading to cancer and infertility, respectively. In females, the study of insect ERVs (IERV) pointed out the overlap between genetics and virology with the genetic-dependent regulation of ZAM and the non-infectious and infectious life cycles of gypsy. The pattern of ERVs expression in rodent, ovine and human females suggest a hormone-dependent mechanism consistent with the mammalian oestrus cycle regulation. The differentiation of the mammary epithelium and breast tumorigenesis involving the mouse mammary tumour viruses (MMTV) illustrate the intimate connection between endogenous and exogenous retroviruses. Last, as a major site of ERVs transcription, placenta contributed to our understanding of ERVs modulation of neighbouring gene expression. As an interface, i.e. a site of conflicts and exchanges, placenta should resist infection and protect the foetus against the maternal immune system. Retroviral envelopes could theoretically provide such features due to receptor interference, immunosuppression and fusion properties, as shown by the HERV-W envelope involved in the syncytiotrophoblast formation. We conclude with an insight on the evolutionary and epigenetic consequences of the relationships of ERV guests with their animal hosts.

Mouse ovary developmental RNA and protein markers from gene expression profiling

To identify genes involved in morphogenetic events during mouse ovary development, we started with microarray analyses of whole organ RNA. Transcripts for 60% of the 15,000 gene NIA panel were detected, and about 2000 were differentially expressed in nascent newborn compared to adult ovary. Highly differentially expressed transcripts included noncoding RNAs and newly detected genes involved in transcription regulation and signal transduction. The phased pattern of newborn mouse ovary differentiation allowed us to (1) extend information on activity and stage specificity of cell type-specific genes; and (2) generate a list of candidate genes involved in primordial follicle formation, including podocalyxin (Podxl), PDGFR-beta, and a follistatin-domain-encoding gene Flst1. Oocyte-specific transcripts included many (e.g., Deltex2, Bicd2, and Zfp37) enriched in growing oocytes, as well as a novel family of untranslated RNA's (RLTR10) that is selectively expressed in early stage follicles. The results indicate that global expression profiling of whole organ RNA provides sensitive first-line information about ovarian histogenesis for which no in vitro cell models are currently available.